A continuous process system such as a steam generator process has many components. The steam generator system includes a boiler that has tubes through which water flows. Because of heat, pressure, and wear over time, the boiler tubes eventually begin to leak, i.e., the beginning of a “leak event.” When a boiler tube(s) starts to leak, steam which flashes over from the water escaping through the leak therein is lost to the boiler environment. In general, the amount of leaked water/steam may be small at the inception of a tube leak event. However, unless the tube is repaired, the leak will continue to grow, i.e., the tube leak rate increases with time until the tube eventually ruptures. Further a rupture in one tube may damage adjacent tubes resulting in a huge overall leak. Thus, once a rupture occurs the utility operating the boiler is forced to shut the boiler down immediately.
Boiler tube failures are a major cause of forced shut downs in fossil power plants. For example, approximately 41,000 tube failures occur every year in the United States alone. The cost of these failures proves to be quite expensive for utilities, exceeding $5 billion a year. [Lind, M. H., “Boiler Tube Leak Detection System,” Proceedings of the Third EPRI Incipient-Failure Detection Conference, EPRI CS-5395, March 1987].
In order to reduce the occurrences of such forced outages, early boiler tube leak detection is highly desirable. Early boiler tube leak detection would allow utilities to schedule a repair at a convenient time rather than to suffer a later forced outage. In addition, the earlier the detection, the better the chances are of limiting damage to adjacent tubes. Additional savings that result from early detection of boiler tube leaks accrue from items such as:    1) Shorter period of heat rate degradation;    2) Less ancillary damage caused by the leakage; and    3) Potential that the leak itself will be smaller if caught sooner.
Various methods are described in the prior art to detect boiler tube leaks. U.S. Pat. Nos. 6,567,795 and 6,192,352 describe a method that uses neural networks and fuzzy math. U.S. Patent Nos. 5,847,266 and 5,363,693 describe a method that uses input/output comparison. U.S. Patent Nos. 4,960,079 and 4,640,121 describe acoustical methods. None of the prior art methods work well due to poor model fidelity and inadequate fault tolerance. For example the acoustical method which detects the noise made by the leaking water must compete with the noisy environment present in the power house. Therefore, the result of the prior art methods are either numerous false alarms or real tube leaks that are not detected.